Magnetoresistive element including layered film touching periphery of spacer layer

ABSTRACT

An MR element includes an MR stack including a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer disposed between the first and the second ferromagnetic layer. The MR stack has an outer surface, and the spacer layer has a periphery located in the outer surface of the MR stack. The magnetoresistive element further includes a layered film that touches the periphery of the spacer layer. The spacer layer includes a semiconductor layer formed using an oxide semiconductor as a material. The layered film includes a first layer, a second layer, and a third layer stacked in this order. The first layer is formed of the same material as the semiconductor layer, and touches the periphery of the spacer layer. The second layer is a metal layer that forms a Schottky barrier at the interface between the first layer and the second layer. The third layer is an insulating layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetoresistive element, a thin-filmmagnetic head including the magnetoresistive element and a method ofmanufacturing the same, and to a head assembly and a magnetic disk driveeach including the magnetoresistive element.

2. Description of the Related Art

Performance improvements in thin-film magnetic heads have been sought asareal recording density of magnetic disk drives has increased. A widelyused type of thin-film magnetic head is a composite thin-film magnetichead that has a structure in which a write head having an induction-typeelectromagnetic transducer for writing and a read head having amagnetoresistive element (that may be hereinafter referred to as MRelement) for reading are stacked on a substrate.

MR elements include GMR (giant magnetoresistive) elements utilizing agiant magnetoresistive effect, and TMR (tunneling magnetoresistive)elements utilizing a tunneling magnetoresistive effect.

Read heads are required to have characteristics of high sensitivity andhigh output. As the read heads that satisfy such requirements, thoseemploying spin-valve GMR elements or TMR elements have beenmass-produced.

A spin-valve GMR element typically includes a free layer, a pinnedlayer, a nonmagnetic conductive layer disposed between the free layerand the pinned layer, and an antiferromagnetic layer disposed on a sideof the pinned layer farther from the nonmagnetic conductive layer. Thefree layer is a ferromagnetic layer having a direction of magnetizationthat changes in response to a signal magnetic field. The pinned layer isa ferromagnetic layer having a fixed direction of magnetization. Theantiferromagnetic layer is a layer that fixes the direction ofmagnetization of the pinned layer by means of exchange coupling with thepinned layer.

Conventional GMR heads have a structure in which a current used fordetecting magnetic signals (hereinafter referred to as a sense current)is fed in the direction parallel to the planes of the layersconstituting the GMR element. Such a structure is called a CIP(current-in-plane) structure. On the other hand, developments have beenpursued for another type of GMR heads having a structure in which thesense current is fed in a direction intersecting the planes of thelayers constituting the GMR element, such as the direction perpendicularto the planes of the layers constituting the GMR element. Such astructure is called a CPP (current-perpendicular-to-plane) structure. AGMR element used for read heads having the CPP structure is hereinaftercalled a CPP-GMR element. A GMR element used for read heads having theCIP structure is hereinafter called a CIP-GMR element.

In recent years, with an increase in recording density, there have beenincreasing demands for a reduction in track width of a read head. Areduction in track width of a read head is achievable by reducing thewidth of the MR element. A reduction in width of the MR element leads toa reduction in length of the MR element taken in the directionperpendicular to the medium facing surface of the thin-film magnetichead. This results in a reduction in area of each of the top surface andthe bottom surface of the MR element.

In a read head of the CIP structure, since shield gap films separate theCIP-GMR element from respective shield layers, a reduction in areas ofthe top and bottom surfaces of the CIP-GMR element results in areduction in heat dissipation efficiency. Consequently, the read head ofthis type has a problem that the operating current is limited so as toensure reliability.

In a read head of the CPP structure, in contrast, no shield gap filmsare required, and there are provided electrode layers touching the topsurface and the bottom surface of the CPP-GMR element, respectively. Theelectrode layers can also function as shield layers. The read head ofthe CPP structure is capable of solving the above-mentioned problem ofthe read head of the CIP structure. In the read head of the CPPstructure, high heat dissipation efficiency is achieved since theelectrode layers touch the top surface and the bottom surface of theCPP-GMR element. Consequently, in the read head of this type it ispossible to increase the operating current. Furthermore, in the readhead of this type, the smaller the areas of the top surface and thebottom surface of the GPP-GMR element, the higher is the resistance ofthe element and accordingly the greater is the magnetoresistance changeamount. The read head of this type therefore allows a reduction in trackwidth.

A typical CPP-GMR element, however, has a disadvantage that it is notsatisfactorily high in magnetoresistance change ratio (hereinafterreferred to as MR ratio), which is a ratio of magnetoresistance changewith respect to the resistance of the element. This is presumablybecause scattering of spin-polarized electrons occurs and spininformation is lost at the interface between the nonmagnetic conductivelayer and a magnetic layer or in the nonmagnetic conductive layer.

Additionally, a CPP-GMR element is low in resistance, and is small inresistance change amount, accordingly. Consequently, in order to obtaina higher read output with a CPP-GMR element, it is necessary to increasethe voltage applied to the element. An increase in the voltage appliedto the element would raise the following problem, however. In a CPP-GMRelement, a current is fed in the direction perpendicular to the plane ofeach layer. This causes spin-polarized electrons to be injected from thefree layer into the pinned layer or from the pinned layer into the freelayer. In the free layer or the pinned layer the spin-polarizedelectrons generate a torque that rotates the magnetization of the layer,that is, a spin torque. The spin torque is proportional to the currentdensity. An increase in the voltage applied to the CPP-GMR elementcauses an increase in current density, thereby resulting in an increasein spin torque. An increase in spin torque results in a problem that thedirection of magnetization of the pinned layer is changed, or a problemthat the free layer becomes unable to freely change the direction ofmagnetization thereof in response to an external magnetic field. To copewith this, as described below, consideration has been given toincreasing the resistance change amount of a CPP-GMR element byincreasing the resistance of the CPP-GMR element.

JP 2003-008102A discloses a CPP-GMR element including: a pinned layerwhose direction of magnetization is fixed; a free layer whose directionof magnetization changes in response to an external magnetic field; anonmagnetic metal intermediate layer provided between the pinned layerand the free layer; and a resistance adjustment layer provided betweenthe pinned layer and the free layer and made of a material containingconductive carriers not more than 10²²/cm³. JP 2003-008102A disclosesthat the material of the resistance adjustment layer is preferably asemiconductor or a semimetal.

JP 2003-298143A discloses an MR element of the CPP structure including apinned layer whose direction of magnetization is fixed, a free layerwhose direction of magnetization changes in response to an externalmagnetic field, and an intermediate layer located between the pinnedlayer and the free layer, wherein the intermediate layer includes afirst layer (an intermediate oxide layer) made of an oxide and having aregion in which the resistance is relatively high and a region in whichthe resistance is relatively low, and wherein, when a sense currentpasses through the first layer, the sense current preferentially flowsthrough the region in which the resistance is relatively low. JP2003-298143A discloses that the sense current has an ohmiccharacteristic when passing through the first layer. Therefore, the MRelement disclosed in this publication is not a TMR element but a CPP-GMRelement. Such a CPP-GMR element is called a current-confined-path typeCPP-GMR element, for example. JP 2003-298143A further discloses that theintermediate layer further includes a second layer (an interfaceadjusting intermediate layer) made of a nonmagnetic metal that isdisposed between the first layer and the pinned layer, and between thefirst layer and the free layer.

JP 2006-261306A also discloses a current-confined-path type CPP-GMRelement. This CPP-GMR element includes an intermediate layer disposedbetween the pinned layer and the free layer. The intermediate layerincludes an insulating film, and a columnar metal conduction portionformed within the insulating film. The CPP-GMR element further includesa compound layer formed between the metal conduction portion and one ofthe pinned layer and the free layer. The compound layer includes acompound having an ionic binding or covalent binding property. Forexample, a III-V semiconductor, a II-VI semiconductor or an oxidesemiconductor is used as the material of the compound layer.

For a CPP-GMR element, providing a spacer layer including a layer madeof a semiconductor between the free layer and the pinned layer isconsidered to be advantageous in suppressing spin toque while making theresistance of the CPP-GMR element be of an appropriate value andincreasing the resistance change amount of the CPP-GMR element.

However, when a thin-film magnetic head including a read head and awrite head was actually fabricated using, for the read head, a CPP-GMRelement with a spacer layer including a layer made of an oxidesemiconductor, a problem was found, that is, a great reduction in MRratio was found to occur when heat was applied to the CPP-GMR elementafter fabrication of the element. Occasions when heat is applied to theelement after its fabrication include, for example, heat treatmentperformed for hardening photoresist covering the coil in the process offabricating the write head, and heating performed in a reliability teston the thin-film magnetic head.

The above-mentioned phenomenon in which the MR ratio is greatly reducedwhen heat is applied to the element after its fabrication did not occurin a typical CPP-GMR element.

Typically, bias magnetic field applying layers for applying a biasmagnetic field to the free layer are respectively provided on both sidesof an MR stack that is a stack of the layers that constitute a GMRelement, the sides being opposed to each other in the track widthdirection. Furthermore, on the peripheral surface of the MR stack, aninsulating layer is provided for insulating the MR stack from the biasmagnetic field applying layers. A CPP-GMR element having such aconfiguration is disclosed in, for example, JP 2005-135514A. JP2005-135514A teaches using A₂O₃ as the material of the foregoinginsulating layer.

A CIP-GMR element having an insulating layer disposed on the peripheralsurface of the MR stack is disclosed in, for example, JP 2004-326853Aand JP 2005-018887A. These publications teach using Al₂O₃ and SiO₂ asthe material of the foregoing insulating layer.

OBJECT AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a magnetoresistiveelement having a spacer layer including a layer made of an oxidesemiconductor, the magnetoresistive element being capable of suppressinga reduction in MR ratio occurring when heat is applied to the elementafter its fabrication, and to provide a thin-film magnetic headincluding this magnetoresistive element and a method of manufacturingthe same, and a head assembly and a magnetic disk drive each includingthe magnetoresistive element.

A magnetoresistive element of the present invention includes an MR stackincluding a first ferromagnetic layer, a second ferromagnetic layer, anda spacer layer disposed between the first ferromagnetic layer and thesecond ferromagnetic layer. In this magnetoresistive element, a currentfor detecting magnetic signals is fed in a direction intersecting theplane of each of the foregoing layers. The MR stack has an outersurface, and the spacer layer has a periphery located in the outersurface of the MR stack. The magnetoresistive element further includes alayered film that touches the periphery of the spacer layer. The spacerlayer includes a semiconductor layer formed using an oxide semiconductoras a material. The layered film includes a first layer, a second layer,and a third layer stacked in this order. The first layer is formed ofthe same material as the semiconductor layer, and touches the peripheryof the spacer layer. The second layer is a metal layer that forms aSchottky barrier at an interface between the first layer and the secondlayer. The third layer is an insulating layer.

In the magnetoresistive element of the invention, the firstferromagnetic layer may be a free layer having a direction ofmagnetization that changes in response to an external magnetic field,while the second ferromagnetic layer may be a pinned layer having afixed direction of magnetization.

In the magnetoresistive element of the invention, the first layer mayhave a thickness within a range of 1 to 6 nm. The second layer may havea thickness within a range of 0.4 to 1.2 nm. The third layer may have athickness of 1 nm or greater. The thickness of each of the first layer,the second layer and the third layer is a dimension of each of theselayers taken in the direction in which the first layer, the second layerand the third layer are stacked.

In the magnetoresistive element of the invention, the material of whichthe semiconductor layer and the first layer are formed may be an oxideof at least one of Zn, In and Sn.

In the magnetoresistive element of the invention, the material of whichthe semiconductor layer and the first layer are formed may be ZnO, whilea material of which the second layer is formed may be any of Os, Ir, Pt,Pd, Ni, Au, Co and Ru.

A first and a second thin-film magnetic head of the present inventioneach include the magnetoresistive element of the invention.Specifically, the first thin-film magnetic head of the inventionincludes: a medium facing surface that faces toward a recording medium;the magnetoresistive element of the invention disposed near the mediumfacing surface to detect a signal magnetic field sent from the recordingmedium; and a pair of electrodes for feeding a current for detectingmagnetic signals to the magnetoresistive element. The second thin-filmmagnetic head of the invention includes a medium facing surface thatfaces toward a recording medium, a read head, and a write head, the readhead including: the magnetoresistive element of the invention disposednear the medium facing surface to detect a signal magnetic field sentfrom the recording medium, and a pair of electrodes for feeding acurrent for detecting magnetic signals to the magnetoresistive element.

A manufacturing method for a thin-film magnetic head of the presentinvention is a method of manufacturing the second thin-film magnetichead of the invention. The method includes the steps of forming the readhead and forming the write head after the read head is formed, whereinthe step of forming the write head includes the step of performing heattreatment.

A head assembly of the present invention includes: a slider includingthe first thin-film magnetic head of the invention and disposed to facetoward a recording medium; and a supporter flexibly supporting theslider.

A magnetic disk drive of the present invention includes: a sliderincluding the first thin-film magnetic head of the invention anddisposed to face toward a recording medium that is driven to rotate; andan alignment device supporting the slider and aligning the slider withrespect to the recording medium.

According to the present invention, the magnetoresistive elementincludes: the MR stack including the first and the second ferromagneticlayer and the spacer layer disposed therebetween; and the layered filmthat touches the periphery of the spacer layer. The spacer layerincludes the semiconductor layer formed using an oxide semiconductor asa material. The layered film includes the first layer, the second layerand the third layer stacked in this order. The first layer is formed ofthe same material as the semiconductor layer, and touches the peripheryof the spacer layer. The second layer is a metal layer that forms aSchottky barrier at the interface between the first layer and the secondlayer. The third layer is an insulating layer. Such a configuration ofthe present invention makes it possible to suppress transfer of oxygenfrom the semiconductor layer to the layered film, and consequently makesit possible to suppress a reduction in MR ratio occurring when heat isapplied to the magnetoresistive element after its fabrication.

Other and further objects, features and advantages of the invention willappear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating a cross section of a readhead including an MR element of an embodiment of the invention parallelto the medium facing surface.

FIG. 2 is a cross-sectional view illustrating a cross section of theread head including the MR element of the embodiment of the inventionperpendicular to the medium facing surface and the substrate.

FIG. 3 is a cross-sectional view illustrating a cross section of athin-film magnetic head of the embodiment of the invention perpendicularto the medium facing surface and the substrate.

FIG. 4 is a cross-sectional view illustrating a cross section of a poleportion of the thin-film magnetic head of the embodiment of theinvention parallel to the medium facing surface.

FIG. 5 is a perspective view illustrating a slider incorporated in ahead gimbal assembly of the embodiment of the invention.

FIG. 6 is a perspective view illustrating a head arm assembly of theembodiment of the invention.

FIG. 7 is an explanatory view for illustrating the main part of amagnetic disk drive of the embodiment of the invention.

FIG. 8 is a top view of the magnetic disk drive of the embodiment of theinvention.

FIG. 9 is an explanatory view illustrating the relationship amongvarious materials in terms of magnitude of work function.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present invention will now be described in detailwith reference to the drawings. Reference is first made to FIG. 3 andFIG. 4 to outline the configuration and a manufacturing method of athin-film magnetic head of the embodiment of the invention. FIG. 3 is across-sectional view illustrating a cross section of the thin-filmmagnetic head perpendicular to the medium facing surface and thesubstrate. FIG. 4 is a cross-sectional view illustrating a cross sectionof a pole portion of the thin-film magnetic head parallel to the mediumfacing surface.

The thin-film magnetic head of the embodiment has a medium facingsurface 20 that faces toward a recording medium. Furthermore, thethin-film magnetic head includes: a substrate 1 made of a ceramicmaterial such as aluminum oxide and titanium carbide (Al₂O₃—TiC); aninsulating layer 2 made of an insulating material such as alumina(Al₂O₃) and disposed on the substrate 1; a first shield layer 3 made ofa magnetic material and disposed on the insulating layer 2; and an MRelement 5 disposed on the first shield layer 3. The MR element 5includes an MR stack 30 and a layered film 4. Detailed descriptions onthe MR stack 30 and the layered film 4 will be provided later.

The magnetic head further includes: two bias magnetic field applyinglayers 6 respectively disposed adjacent to two side surfaces of the MRstack 30 with the layered film 4 in between; and an insulating layer 7disposed around the MR stack 30 and the bias magnetic field applyinglayers 6. The MR element 5 is disposed near the medium facing surface20. The insulating layer 7 is made of an insulating material such asalumina.

The thin-film magnetic head further includes: a second shield layer 8made of a magnetic material and disposed on the MR element 5, the biasmagnetic field applying layers 6 and the insulating layer 7; aseparating layer 18 made of a nonmagnetic material such as alumina anddisposed on the second shield layer 8; and a bottom pole layer 19 madeof a magnetic material and disposed on the separating layer 18. Themagnetic material used for the second shield layer 8 and the bottom polelayer 19 is a soft magnetic material such as NiFe, CoFe, CoFeB, CoFeNior FeN. Alternatively, a second shield layer that also functions as abottom pole layer may be provided in place of the second shield layer 8,the separating layer 18 and the bottom pole layer 19.

The thin-film magnetic head further includes a write gap layer 9 made ofa nonmagnetic material such as alumina and disposed on the bottom polelayer 19. A contact hole 9 a is formed in a region of the write gaplayer 9 away from the medium facing surface 20.

The thin-film magnetic head further includes a first layer portion 10 ofa thin-film coil disposed on the write gap layer 9. The first layerportion 10 is made of a conductive material such as copper (Cu). In FIG.3, numeral 10 a indicates a connecting portion of the first layerportion 10 connected to a second layer portion 15 of the thin-film coilto be described later. The first layer portion 10 is wound around thecontact hole 9 a.

The thin-film magnetic head further includes: an insulating layer 11made of an insulating material and disposed to cover the first layerportion 10 of the thin-film coil and the write gap layer 9 around thefirst layer portion 10; a top pole layer 12 made of a magnetic material;and a connecting layer 13 made of a conductive material and disposed onthe connecting portion 10 a. The connecting layer 13 may be made of amagnetic material. Each of the outer and the inner edge portion of theinsulating layer 11 is in the shape of a rounded slope.

The top pole layer 12 includes a track width defining layer 12 a, acoupling portion layer 12 b and a yoke portion layer 12 c. The trackwidth defining layer 12 a is disposed on the write gap layer 9 and theinsulating layer 11 over a region extending from a sloped portion of theinsulating layer 11 closer to the medium facing surface 20 to the mediumfacing surface 20. The track width defining layer 12 a includes: afront-end portion that is formed on the write gap layer 9 and functionsas the pole portion of the top pole layer 12; and a connecting portionthat is formed on the sloped portion of the insulating layer 11 closerto the medium facing surface 20 and is connected to the yoke portionlayer 12 c. The front-end portion has a width equal to the write trackwidth. The connecting portion has a width greater than the width of thefront-end portion.

The coupling portion layer 12 b is disposed on a region of the bottompole layer 19 where the contact hole 9 a is formed. The yoke portionlayer 12 c couples the track width defining layer 12 a and the couplingportion layer 12 b to each other. An end of the yoke portion layer 12 cthat is closer to the medium facing surface 20 is located apart from themedium facing surface 20. The yoke portion layer 12 c is connected tothe bottom pole layer 19 through the coupling portion layer 12 b.

The thin-film magnetic head further includes an insulating layer 14 madeof an inorganic insulating material such as alumina and disposed aroundthe coupling portion layer 12 b. The track width defining layer 12 a,the coupling portion layer 12 b, the connecting layer 13 and theinsulating layer 14 have flattened top surfaces.

The thin-film magnetic head further includes the second layer portion 15of the thin-film coil disposed on the insulating layer 14. The secondlayer portion 15 is made of a conductive material such as copper (Cu).In FIG. 3, numeral 15 a indicates a connecting portion of the secondlayer portion 15 that is connected to the connecting portion 10 a of thefirst layer portion 10 of the thin-film coil through the connectinglayer 13. The second layer portion 15 is wound around the couplingportion layer 12 b.

The thin-film magnetic head further includes an insulating layer 16disposed to cover the second layer portion 15 of the thin-film coil andthe insulating layer 14 around the second layer portion 15. Each of theouter and the inner edge portion of the insulating layer 16 is in theshape of a rounded slope. Part of the yoke portion layer 12 c isdisposed on the insulating layer 16.

The thin-film magnetic head further includes an overcoat layer 17disposed to cover the top pole layer 12. The overcoat layer 17 is madeof alumina, for example.

The method of manufacturing the thin-film magnetic head of theembodiment will now be outlined. In the method of manufacturing thethin-film magnetic head of the embodiment, first, the insulating layer 2is formed to have a thickness of 0.2 to 5 μm, for example, on thesubstrate 1 by sputtering or the like. Next, on the insulating layer 2,the first shield layer 3 is formed into a predetermined pattern byplating, for example. Next, although not shown, an insulating layer madeof alumina, for example, is formed over the entire surface. Next, theinsulating layer is polished by chemical mechanical polishing(hereinafter referred to as CMP), for example, until the first shieldlayer 3 is exposed, and the top surfaces of the first shield layer 3 andthe insulating layer are thereby flattened.

Next, the MR element 5, the two bias magnetic field applying layers 6and the insulating layer 7 are formed on the first shield layer 3. Next,the second shield layer 8 is formed on the MR element 5, the biasmagnetic field applying layers 6 and the insulating layer 7. The secondshield layer 8 is formed by plating or sputtering, for example. Next,the separating layer 18 is formed on the second shield layer 8 bysputtering, for example. Next, the bottom pole layer 19 is formed on theseparating layer 18 by plating or sputtering, for example.

Next, the write gap layer 9 is formed to have a thickness of 50 to 300nm, for example, on the bottom pole layer 19 by sputtering or the like.Next, in order to make a magnetic path, the contact hole 9 a is formedby partially etching the write gap layer 9 at a center portion of thethin-film coil that will be formed later.

Next, the first layer portion 10 of the thin-film coil is formed to havea thickness of 2 to 3 μm, for example, on the write gap layer 9. Thefirst layer portion 10 is wound around the contact hole 9 a.

Next, the insulating layer 11 made of an organic insulating material isformed into a predetermined pattern to cover the first layer portion 10of the thin-film coil and the write gap layer 9 disposed around thefirst layer portion 10. The organic insulating material used for theinsulating layer 11 is a material that exhibits fluidity with anincrease in temperature and thereafter hardens, such as photoresist.Next, the insulating layer 11 is heat-treated at a temperature of, e.g.,250° C., so as to flatten the surface of the insulating layer 11 and toharden the insulating layer 11. Through this heat treatment, the outerand the inner edge portion of the insulating layer 11 are each broughtinto the shape of a rounded slope.

Next, the track width defining layer 12 a of the top pole layer 12 isformed on the write gap layer 9 and the insulating layer 11 over theregion extending from the sloped portion of the insulating layer 11closer to the medium facing surface 20 described later to the mediumfacing surface 20.

When the track width defining layer 12 a is formed, the coupling portionlayer 12 b is formed on the region of the bottom pole layer 19 where thecontact hole 9 a is formed, and the connecting layer 13 is formed on theconnecting portion 10 a at the same time.

Next, pole trimming is performed. That is, in a region around the trackwidth defining layer 12 a, the write gap layer 9 and at least part ofthe pole portion of the bottom pole layer 19 close to the write gaplayer 9 are etched using the track width defining layer 12 a as a mask.This provides a trim structure in which, as shown in FIG. 4, the poleportion of the top pole layer 12, the write gap layer 9, and at leastpart of the pole portion of the bottom pole layer 19 have equal widths.The trim structure allows prevention of an increase in effective trackwidth resulting from an expansion of magnetic flux near the write gaplayer 9.

Next, the insulating layer 14 is formed to have a thickness of 3 to 4μm, for example, over the entire top surface of a stack of the layersthat have been formed through the foregoing steps. Next, the insulatinglayer 14 is polished by CMP, for example, to reach the surfaces of thetrack width defining layer 12 a, the coupling portion layer 12 b and theconnecting layer 13, and is thereby flattened.

Next, the second layer portion 15 of the thin-film coil is formed tohave a thickness of 2 to 3 μm, for example, on the insulating layer 14that has been flattened. The second layer portion 15 is wound around thecoupling portion layer 12 b.

Next, the insulating layer 16 made of an organic insulating material isformed into a predetermined pattern to cover the second layer portion 15of the thin-film coil and the insulating layer 14 disposed around thesecond layer portion 15. The organic insulating material used for theinsulating layer 16 is a material that exhibits fluidity with anincrease in temperature and thereafter hardens, such as photoresist.Next, the insulating layer 16 is heat-treated at a temperature of, e.g.,250° C., so as to flatten the surface of the insulating layer 16 and toharden the insulating layer 16. Through this heat treatment, the outerand the inner edge portion of the insulating layer 16 are each broughtinto the shape of a rounded slope. Next, the yoke portion layer 12 c isformed on the track width defining layer 12 a, the insulating layers 14and 16 and the coupling portion layer 12 b.

Next, the overcoat layer 17 is formed to cover the entire top surface ofa stack of the layers that have been formed through the foregoing steps.Wiring, terminals and so on are then formed on the overcoat layer 17.Finally, machining of the slider including the foregoing layers isperformed to form the medium facing surface 20. The thin-film magnetichead including a write head and a read head is thus completed.

As described above, this embodiment includes the step of forming theread head and the step of forming the write head after the read head isformed. The step of forming the write head includes the step ofperforming heat treatment.

The thin-film magnetic head manufactured in this manner has the mediumfacing surface 20 that faces toward the recording medium, the read head,and the write head. The read head is disposed near the medium facingsurface 20 to detect a signal magnetic field sent from the recordingmedium. The configuration of the read head will be described in detaillater.

The write head includes: the bottom pole layer 19 and the top pole layer12 magnetically coupled to each other and including the respective poleportions that are opposed to each other and placed in regions of thepole layers on a side of the medium facing surface 20; the write gaplayer 9 provided between the pole portion of the bottom pole layer 19and the pole portion of the top pole layer 12; and the thin-film coil10, 15 at least part of which is placed between the bottom pole layer 19and the top pole layer 12 and insulated from the bottom pole layer 19and the top pole layer 12. In this thin-film magnetic head, asillustrated in FIG. 3, the length from the medium facing surface 20 tothe end of the insulating layer 11 closer to the medium facing surface20 corresponds to throat height TH. Note that the throat height refersto a length (height) from the medium facing surface 20 to a point atwhich the distance between the two pole layers starts to increase. Itshould be noted that, while FIG. 3 and FIG. 4 illustrate a write headfor use with the longitudinal magnetic recording system, the write headof the embodiment can be one for use with the perpendicular magneticrecording system.

Reference is now made to FIG. 1 and FIG. 2 to describe the configurationof the read head of the embodiment in detail. FIG. 1 is across-sectional view illustrating a cross section of the read headparallel to the medium facing surface. As illustrated in FIG. 1, theread head includes the first shield layer 3 and the second shield layer8 disposed at a specific distance from each other, and the MR element 5disposed between the first shield layer 3 and the second shield layer 8.The MR element 5 and the second shield layer 8 are stacked on the firstshield layer 3. The MR element 5 includes the MR stack 30 and thelayered film 4. The MR stack 30 has an outer surface including a topsurface 30 a, a bottom surface 30 b, and a peripheral surface 30 c thatconnects the top surface 30 a and the bottom surface 30 b to each other.The peripheral surface 30 c of the MR stack 30 includes an end facelocated in the medium facing surface 20, an end face opposite to themedium facing surface 20, and two side surfaces that couple these twoend faces to each other. Of the peripheral surface 30 c of the MR stack30, the layered film 4 touches the two side surfaces and the end faceopposite to the medium facing surface 20, and does not touch the endface located in the medium facing surface 20.

The read head further includes: the two bias magnetic field applyinglayers 6 that are respectively disposed adjacent to the two sidesurfaces of the MR stack 30 with the layered film 4 in between and thatapply a bias magnetic field to the MR stack 30; and the insulating layer7 disposed around the MR stack 30 and the bias magnetic field applyinglayers 6. As illustrated in FIG. 1 and FIG. 2, the layered film 4 islocated between the peripheral surface 30 c of the MR stack 30 and thebias magnetic field applying layers 6, between the first shield layer 3and the bias magnetic field applying layers 6, between the peripheralsurface 30 c of the MR stack 30 and the insulating layer 7, and betweenthe first shield layer 3 and the insulating layer 7.

The bias magnetic field applying layers 6 are each formed of a hardmagnetic layer (hard magnet) or a stack of a ferromagnetic layer and anantiferromagnetic layer, for example. To be specific, the bias magneticfield applying layers 6 are made of CoPt or CoCrPt, for example.

The MR element 5 of the embodiment is a CPP-GMR element. In this MRelement 5, a sense current, which is a current for detecting magneticsignals, is fed in a direction intersecting the planes of layersconstituting the MR stack 30, such as the direction perpendicular to theplanes of the layers constituting the MR stack 30. The first shieldlayer 3 and the second shield layer 8 also function as a pair ofelectrodes for feeding the sense current to the MR element 5 in adirection intersecting the planes of the layers constituting the MRstack 30, such as the direction perpendicular to the planes of thelayers constituting the MR stack 30. Alternatively, besides the firstshield layer 3 and the second shield layer 8, there may be provided apair of electrodes on top and bottom of the MR stack 30, respectively.The MR element 5 has a resistance that changes in response to anexternal magnetic field, that is, a signal magnetic field sent from therecording medium. The resistance of the MR element 5 can be determinedfrom the sense current. It is thus possible to read data stored on therecording medium through the use of the read head.

FIG. 1 and FIG. 2 illustrate an example of configuration of the MRelement 5. As previously mentioned, the MR element 5 includes the MRstack 30. The MR stack 30 includes: a free layer 25 that is aferromagnetic layer having a direction of magnetization that changes inresponse to the signal magnetic field; a pinned layer 23 that is aferromagnetic layer having a fixed direction of magnetization; and aspacer layer 24 disposed between the free layer 25 and the pinned layer23. The free layer 25 corresponds to the first ferromagnetic layer ofthe present invention, while the pinned layer 23 corresponds to thesecond ferromagnetic layer of the present invention. In the exampleillustrated in FIG. 1 and FIG. 2, the pinned layer 23 is disposed closerto the first shield layer 3 than is the free layer 25. However, thereverse is possible, that is, the free layer 25 can be disposed closerto the first shield layer 3.

The MR stack 30 further includes: an antiferromagnetic layer 22 disposedon a side of the pinned layer 23 farther from the spacer layer 24; anunderlying layer 21 disposed between the first shield layer 3 and theantiferromagnetic layer 22; and a protection layer 26 disposed betweenthe free layer 25 and the second shield layer 8. In the MR element 5illustrated in FIG. 1 and FIG. 2, the underlying layer 21, theantiferromagnetic layer 22, the pinned layer 23, the spacer layer 24,the free layer 25 and the protection layer 26 are stacked in this orderon the first shield layer 3.

The antiferromagnetic layer 22 is a layer for fixing the direction ofmagnetization of the pinned layer 23 by means of exchange coupling withthe pinned layer 23. The underlying layer 21 is provided for improvingthe crystallinity and orientability of each layer formed thereon andparticularly for enhancing the exchange coupling between theantiferromagnetic layer 22 and the pinned layer 23. The protection layer26 is a layer for protecting the layers located therebelow.

The underlying layer 21 has a thickness of 1 to 6 nm, for example. Theunderlying layer 21 is formed of a stack of a Ta layer and a Ru layer,for example.

The antiferromagnetic layer 22 has a thickness of 4 to 30 nm, forexample. The antiferromagnetic layer 22 is formed of anantiferromagnetic material containing Mn and at least one element M_(II)selected from the group consisting of Pt, Ru, Rh, Pd, Ni, Cu, Ir, Cr andFe, for example. The Mn content of the material is preferably equal toor higher than 35 atomic percent and lower than or equal to 95 atomicpercent, while the content of the other element M_(II) of the materialis preferably equal to or higher than 5 atomic percent and lower than orequal to 65 atomic percent. There are two types of the antiferromagneticmaterial, one is a non-heat-induced antiferromagnetic material thatexhibits antiferromagnetism without any heat treatment and induces anexchange coupling magnetic field between a ferromagnetic material anditself, and the other is a heat-induced antiferromagnetic material thatexhibits antiferromagnetism by undergoing heat treatment. Theantiferromagnetic layer 22 can be formed of either of these types.Examples of the non-heat-induced antiferromagnetic material include a Mnalloy that has a γ phase, such as RuRhMn, FeMn, or IrMn. Examples of theheat-induced antiferromagnetic material include a Mn alloy that has aregular crystal structure, such as PtMn, NiMn, or PtRhMn.

As a layer for fixing the direction of magnetization of the pinned layer23, a hard magnetic layer formed of a hard magnetic material such asCoPt may be provided in place of the antiferromagnetic layer 22described above. In this case, for example, Cr, CrTi or TiW is used asthe material of the underlying layer 21.

In the pinned layer 23, the direction of magnetization is fixed byexchange coupling with the antiferromagnetic layer 22 at the interfacebetween the antiferromagnetic layer 22 and the pinned layer 23. Thepinned layer 23 of the embodiment is a so-called synthetic pinned layer,having an outer layer 31, a nonmagnetic middle layer 32 and an innerlayer 33 that are stacked in this order on the antiferromagnetic layer22. Each of the outer layer 31 and the inner layer 33 includes aferromagnetic layer formed of a ferromagnetic material containing atleast Co selected from the group consisting of Co and Fe, for example.The outer layer 31 and the inner layer 33 are antiferromagnetic-coupledto each other via the nonmagnetic middle layer 32, and themagnetizations thereof are fixed to opposite directions. The outer layer31 has a thickness of 2 to 7 nm, for example. The inner layer 33 has athickness of 2 to 10 nm, for example.

The nonmagnetic middle layer 32 has a thickness of 0.35 to 1.0 nm, forexample. The nonmagnetic middle layer 32 is formed of a nonmagneticmaterial containing at least one element selected from the groupconsisting of Ru, Rh, Ir, Re, Cr, Zr and Cu, for example. Thenonmagnetic middle layer 32 is provided for producing antiferromagneticexchange coupling between the inner layer 33 and the outer layer 31, andfor fixing the magnetizations of the inner layer 33 and the outer layer31 to opposite directions. It should be noted that the magnetizations ofthe inner layer 33 and the outer layer 31 in opposite directions includenot only a case in which there is a difference of 180 degrees betweenthese directions of magnetizations, but also a case in which there is adifference in the range of 180 plus/minus about 20 degrees between them.

The spacer layer 24 has a periphery 24 a located in the peripheralsurface 30 c of the outer surface of the MR stack 30. The spacer layer24 includes: a first nonmagnetic metal layer 41 and a second nonmagneticmetal layer 43 each formed of a nonmagnetic metal material; and asemiconductor layer 42 formed using an oxide semiconductor as a materialand disposed between the first nonmagnetic metal layer 41 and the secondnonmagnetic metal layer 43. The first nonmagnetic metal layer 41 touchesthe inner layer 33, while the second nonmagnetic metal layer 43 touchesthe free layer 25.

The oxide semiconductor used as the material of which the semiconductorlayer 42 is formed may be an oxide of at least one of Zn, In, and Sn.Consequently, the material of which the semiconductor layer 42 is formedmay be at least one of ZnO, In₂O₃, and SnO₂. ZnO is known to be turnedinto an n-type semiconductor by electrons released from interstitialzinc or oxygen vacancies. The material of which the semiconductor layer42 is formed may be an oxide semiconductor including two or moremetallic elements selected from Zn, In, and Sn. The semiconductor layer42 has a thickness preferably within a range of 1 to 2 nm, and morepreferably within a range of 1.2 to 1.8 nm.

The nonmagnetic metal material used for the nonmagnetic metal layers 41and 43 can be one of Cu, Au, Ag, Zn, AuCu, CuZn, Cr, Ru, and Rh, forexample. Of these, Cu, Au, and Ag are preferable, of which Cu isparticularly preferable, as the nonmagnetic metal material used for thenonmagnetic metal layers 41 and 43. Each of the nonmagnetic metal layers41 and 43 preferably has a thickness within a range of 0.3 to 2 nm.

The free layer 25 has a thickness of 2 to 10 nm, for example. The freelayer 25 is formed of a ferromagnetic layer having a low coercivity. Thefree layer 25 may include a plurality of ferromagnetic layers stacked.

The protection layer 26 has a thickness of 0.5 to 20 nm, for example.The protection layer 26 may be formed of a Ta layer or a Ru layer, forexample. The protection layer 26 may be formed into a two-layerstructure made up of a combination of a Ta layer and a Ru layer, forexample, or a three-layer structure made up of a combination of Ta, Ruand Ta layers or a combination of Ru, Ta and Ru layers, for example.

At least one of the inner layer 33 and the free layer 25 may include analloy layer having a spin polarization nearly equal to 1, such as aHeusler alloy layer.

The plane geometry of each of the layers 21 to 26 constituting the MRstack 30 is rectangular. The peripheral surface 30 c of the MR stack 30is made up of the peripheries of the layers 21 to 26.

The layered film 4 touches the peripheral surface 30 c of the MR stack30 including the periphery 24 a of the spacer layer 24. The layered film4 includes a first layer 4A, a second layer 4B and a third layer 4Cstacked in this order on the peripheral surface 30 c of the MR stack 30including the periphery 24 a of the spacer layer 24. The first layer 4Ais formed of the same material as the semiconductor layer 42, that is,an oxide semiconductor, and touches the peripheral surface 30 c of theMR stack 30 including the periphery 24 a of the spacer layer 24. Thesecond layer 4B is a metal layer that forms a Schottky barrier at theinterface 4AB between the first layer 4A and the second layer 4B. Thereason for forming a Schottky barrier at the interface 4AB between thefirst layer 4A and the second layer 4B will be described in detaillater. The third layer 4C is an insulating layer. Of the peripheralsurface 30 c of the MR stack 30, the layered film 4 touches the two sidesurfaces and the end face opposite to the medium facing surface 20, anddoes not touch the end face located in the medium facing surface 20.

The first layer 4A preferably has a thickness within a range of 1 to 6nm. The second layer 4B preferably has a thickness within a range of 0.4to 1.2 nm. The third layer 4C preferably has a thickness of 1 nm orgreater.

If the oxide semiconductor used as the material of which the first layer4A is formed is an n-type semiconductor such as ZnO, it is preferredthat the material of which the second layer 4B is formed have a workfunction higher than that of the material of which the first layer 4A isformed. Assuming that the interface 4AB between the first layer 4A andthe second layer 4B is an ideal interface at which no oxide film or nosurface states are present, a Schottky barrier is formed at theinterface 4AB between the first layer 4A and the second layer 4B if thematerial of which the second layer 4B is formed is higher in workfunction than the material of which the first layer 4A is formed. Table1 below lists the work functions of various materials. FIG. 9illustrates the relationship among various materials in terms ofmagnitude of work function. Note that ITO on Table 1 represents indiumtin oxide formed by mixing In₂O₃ with 5 atomic percent SnO₂.

TABLE 1 Material Work function (eV) Os 5.93 Ir 5.76 Pt 5.64 Pd 5.55 Ni5.15 Au 5.1 Co 5 Ru 4.71 Fe 4.5 Cu 4.65 Al 4.28 Ag 4.26 Mg 3.66 MgO 3.55ZnO 4.88 SnO₂ 4.30 In₂O₃ 5.00 ITO 4.70

As can be seen from Table 1 and FIG. 9, the work function of each of Os,Ir, Pt, Pd, Ni, Au and Co is higher than the work function of ZnO.Therefore, in the case where ZnO is used as the material to form thesemiconductor layer 42 and the first layer 4A, using any of Os, Ir, Pt,Pd, Ni, Au and Co as the material to form the second layer 4B enablesformation of a Schottky barrier at the interface 4AB between the firstlayer 4A and the second layer 4B.

Furthermore, as can be seen from Table 1 and FIG. 9, the work functionof Ru is lower than the work function of ZnO. In actuality, however, aSchottky barrier is formed at the interface 4AB between the first layer4A and the second layer 4B even when Ru is used as the material to formthe second layer 4B while ZnO is used as the material to form thesemiconductor layer 42 and the first layer 4A. This is presumablybecause the interface 4AB between the first layer 4A and the secondlayer 4B in actuality is not the ideal one described previously, andthere exist surface states at the interface 4AB between the first layer4A and the second layer 4B. As widely known, when surface states areformed at an interface between a metal and a semiconductor, the actualbarrier height at the interface between the metal and the semiconductoris not determined only by the difference between the work functions ofthe metal and the semiconductor, but also depends on the surface states.As mentioned above, when ZnO is the material used to form thesemiconductor layer 42 and the first layer 4A, a Schottky barrier can beformed at the interface 4AB between the first layer 4A and the secondlayer 4B even in the case where Ru is used as the material to form thesecond layer 4B. Consequently, when ZnO is the material used to form thesemiconductor layer 42 and the first layer 4A, it is possible to use anyof Os, Ir, Pt, Pd, Ni, Au, Co and Ru as the material to form the secondlayer 4B.

In the case where a material other than ZnO, such as SnO₂, In₂O₃ or ITOlisted on Table 1, is used to form the semiconductor layer 42 and thefirst layer 4A, too, it is possible to form a Schottky barrier at theinterface 4AB between the first layer 4A and the second layer 4B byforming the second layer 4B using a material that is higher in workfunction than the material used to form the first layer 4A.

The third layer is preferably formed of an inorganic insulatingmaterial. The inorganic insulating material can be Al₂O₃ or SiO₂, forexample.

The MR element 5 of the embodiment preferably has a resistance-areaproduct (hereinafter referred to as RA) within a range of 0.1 to 0.3Ω·μm².

A method of manufacturing the read head illustrated in FIG. 1 and FIG. 2will now be described. In the method of manufacturing the read head,first, the first shield layer 3 having a predetermined pattern is formedon the insulating layer 2 by plating, for example. Next, on the firstshield layer 3, films to become the respective layers constituting theMR stack 30 are formed in succession by sputtering, for example, tothereby form a multilayer film for the MR stack 30. The film to becomethe semiconductor layer 42 may be formed by sputtering a material of theoxide semiconductor used for the semiconductor layer 42 by DCsputtering, for example, or by sputter-forming a film of a metal thatwill become an oxide semiconductor through oxidation and then oxidizingthis metal film by plasma oxidation or natural oxidation, for example.

Next, the foregoing multilayer film for the MR stack 30 is subjected toheat treatment. This heat treatment is performed for the purpose ofimproving the crystallinity of the semiconductor layer 42 and directingthe magnetization of the pinned layer 23 to one direction. Thetemperature of this heat treatment is preferably within a range of 200°C. to 300° C., and more preferably within a range of 250° C. to 290° C.Next, the multilayer film for the MR stack 30 is patterned by etching tothereby form the MR stack 30.

Next, the layered film 4 is formed by forming the first layer 4A, thesecond layer 4B and the third layer 4C in this order. The MR element 5is thereby completed. The first layer 4A may be formed by sputtering amaterial of the oxide semiconductor used for the first layer 4A, or bysputter-forming a film of a metal that will become an oxidesemiconductor through oxidation and then oxidizing this metal film byplasma oxidation or natural oxidation, for example. The second layer 4Band the third layer 4C are formed by sputtering, for example.

Next, the bias magnetic field applying layers 6 are formed. Next, thesecond shield layer 8 is formed by plating or sputtering, for example,on the MR element 5 and the bias magnetic field applying layers 6.

The operation of the thin-film magnetic head of the embodiment will nowbe described. The thin-film magnetic head writes data on a recordingmedium by using the write head and reads data written on the recordingmedium by using the read head.

In the read head, the direction of the bias magnetic field produced bythe bias magnetic field applying layers 6 intersects the directionperpendicular to the medium facing surface 20 at a right angle. In theMR element 5, when no signal magnetic field is present, the direction ofmagnetization of the free layer 25 is aligned with the direction of thebias magnetic field. On the other hand, the direction of magnetizationof the pinned layer 23 is fixed to the direction perpendicular to themedium facing surface 20.

In the MR element 5, the direction of magnetization of the free layer 25changes in response to a signal magnetic field sent from the recordingmedium. This causes a change in the relative angle between the directionof magnetization of the free layer 25 and the direction of magnetizationof the pinned layer 23, and as a result, the resistance of the MRelement 5 changes. The resistance of the MR element 5 can be determinedfrom the potential difference between the first and second shield layers3 and 8 produced when a sense current is fed to the MR element 5 fromthe shield layers 3 and 8. Thus, it is possible for the read head toread data stored on the recording medium.

In the MR element 5 of the embodiment, the spacer layer 24 includes thetwo nonmagnetic metal layers 41 and 43 and the semiconductor layer 42disposed between the two layers. According to the embodiment, it istherefore possible for the MR element 5 to attain a greater RA andaccordingly a greater resistance change amount, compared with a casewhere the spacer layer 24 does not include the semiconductor layer 42.

As will be seen from experimental results described later, in an MRelement having an insulating layer made of Al₂O₃ instead of the layeredfilm 4 of the embodiment, there occurs the problem that the MR ratio isgreatly reduced when heat is applied to the MR element after itsfabrication. Occasions when heat is applied to the MR element after itsfabrication include, for example, heat treatment for hardeningphotoresist to form the insulating layer 11 covering the coil 10 andheat treatment for hardening photoresist to form the insulating layer 16covering the coil 15, which are performed in the process of fabricatingthe write head. Another occasion when heat is applied to the MR elementafter its fabrication is heating performed in a reliability test on thethin-film magnetic head. In the case of the MR element having aninsulating layer of Al₂O₃ instead of the layered film 4 of theembodiment as mentioned above, a possible reason why the MR ratio isgreatly reduced when heat is applied to the MR element after itsfabrication would be because, when heat is applied to the MR element,there occurs a transfer of elements such as oxygen from thesemiconductor layer 42 formed of an oxide semiconductor to theinsulating layer, and this results in degradation in quality of thecrystal of the semiconductor layer 42.

According to the embodiment, in contrast, the layered film 4 is disposedto touch the peripheral surface 30 c of the MR stack 30 including theperiphery 24 a of the spacer layer 24. The layered film 4 includes thefirst layer 4A, the second layer 4B and the third layer 4C stacked inthis order on the peripheral surface 30 c of the MR stack 30 includingthe periphery 24 a of the spacer layer 24. The first layer 4A is formedof the same material (oxide semiconductor) as the semiconductor layer42, and touches the peripheral surface 30 c of the MR stack 30 includingthe periphery 24 a of the spacer layer 24. The second layer 4B is ametal layer that forms a Schottky barrier at the interface 4AB betweenthe first layer 4A and the second layer 4B. The third layer 4C is aninsulating layer. According to the embodiment, the first layer 4A formedof the same material as the semiconductor layer 42 touches theperipheral surface 30 c of the MR stack 30 including the periphery 24 aof the spacer layer 24. It is thereby possible to suppress transfer ofoxygen between the semiconductor layer 42 and the first layer 4A formedof the same material. Consequently, according to the embodiment, it ispossible to suppress transfer of oxygen from the semiconductor layer 42to the layered film 4 and to thereby suppress degradation in quality ofthe crystal of the semiconductor layer 42. The embodiment thus makes itpossible to suppress a reduction in MR ratio occurring when heat isapplied to the MR element 5 after fabrication of the MR element 5.

According to the embodiment, a Schottky barrier is formed at theinterface 4AB between the first layer 4A and the second layer 4B. It isthereby possible to suppress leakage of a current from the MR stack 30to the bias magnetic field applying layers 6 via the layered film 4.Consequently, according to the embodiment, it is possible to establishinsulation between the MR stack 30 and the bias magnetic field applyinglayers 6 without greatly thickening the third layer 4C that is aninsulating layer. This makes it possible to reduce the distance betweenthe free layer 25 and the bias magnetic field applying layers 6 and tothereby improve the stability of the direction of magnetization of thefree layer 25.

In the embodiment, as previously described, in the case where ZnO is thematerial used to form the semiconductor layer 42 and the first layer 4A,it is possible to use any of Os, Ir, Pt, Pd, Ni, Au, Co and Ru as thematerial to form the second layer 4B. Each of these is a metal resistantto oxidizing. Therefore, by using any of these as the material to formthe second layer 4B, it is possible to suppress transfer of oxygen fromthe first layer 4A to the second layer 4B. This also contributes tosuppression of transfer of oxygen from the semiconductor layer 42 to thelayered film 4.

A description will now be given of the results of an experimentperformed for showing the effects of the embodiment. In the experiment,22 types of MR element samples labeled as A1 to A18 and B1 to B4 wereprepared. Each of the samples A1 to A18 corresponds to an example of theMR element 5 of the embodiment. Each of the samples B1 to B4 correspondsto a comparative example against the MR element 5 of the embodiment.Table 2 below shows the specific film configuration of the MR stack 30of the samples A1 to A18 and B1 to B4.

TABLE 2 Layer Substance Thickness (nm) Protection layer Ru 10 Free layerCoFe 4 Spacer Second nonmagnetic metal layer Cu 0.7 layer Semiconductorlayer Oxide semi- 1.7 or 1.8 conductor First nonmagnetic metal layer Cu0.7 Pinned Inner layer CoFe 3.5 layer Nonmagnetic middle layer Ru 0.8Outer layer CoFe 3 Antiferromagnetic layer IrMn 5 Underlying layer Ru 2Ta 1

Table 3 below shows the materials and thicknesses of the semiconductorlayer 42, the first layer 4A, the second layer 4B and the third layer 4Cfor each of the samples A1 to A18 and B1 to B4. The sample B1 isprovided with a single insulating film in place of the layered film 4 ofthe embodiment. On Table 3, for the sample B1 the material and thicknessof the insulating film are entered in the “first layer” columns. Thesample B3 is provided with a semiconductor film and an insulating film,in place of the layered film 4 of the embodiment, that are stacked inthis order on the peripheral surface 30 c of the MR stack 30. On Table3, for the sample B3 the material and thickness of the semiconductorfilm are entered in the “first layer” columns, while the material andthickness of the insulating film are entered in the “third layer”columns. On Table 3, ITO represents indium tin oxide formed by mixingIn₂O₃ with 5 atomic percent SnO₂.

TABLE 3 Semiconductor layer First layer Second layer Third layerThickness Thickness Thickness Thickness Sample Material (nm) Material(nm) Material (nm) Material (nm) B1 ZnO 1.7 Al₂O₃ 6.0 A1 ZnO 1.7 ZnO 3.0Pt 0.7 Al₂O₃ 2.0 A2 ZnO 1.7 ZnO 3.0 Pd 0.7 Al₂O₃ 2.0 A3 ZnO 1.7 ZnO 3.0Au 0.7 Al₂O₃ 2.0 A4 ZnO 1.7 ZnO 3.0 Ir 0.7 Al₂O₃ 2.0 A5 ZnO 1.7 ZnO 3.0Os 0.7 Al₂O₃ 2.0 A6 ZnO 1.7 ZnO 3.0 Ru 0.7 Al₂O₃ 2.0 A7 ZnO 1.7 ZnO 3.0Pt 0.4 Al₂O₃ 2.0 A8 ZnO 1.7 ZnO 3.0 Pt 1.0 Al₂O₃ 2.0 A9 ZnO 1.7 ZnO 3.0Pt 1.2 Al₂O₃ 2.0 A10 ZnO 1.7 ZnO 3.0 Pt 0.7 Al₂O₃ 1.0 B2 ZnO 1.7 ZnO 3.0Pt 0.7 Al₂O₃ 0.5 B3 ZnO 1.7 ZnO 3.0 Al₂O₃ 1.0 A11 In₂O₃ 1.8 In₂O₃ 3.0 Pt0.7 Al₂O₃ 2.0 A12 In₂O₃ 1.8 In₂O₃ 3.0 Ir 0.7 Al₂O₃ 2.0 A13 ITO 1.8 ITO3.0 Pt 0.7 Al₂O₃ 2.0 A14 ITO 1.8 ITO 3.0 Ir 0.7 Al₂O₃ 2.0 A15 SnO₂ 1.8SnO₂ 3.0 Pt 0.7 Al₂O₃ 2.0 A16 SnO₂ 1.8 SnO₂ 3.0 Ir 0.7 Al₂O₃ 2.0 B4 ZnO1.7 ZnO 0.5 Pt 0.7 Al₂O₃ 2.0 A17 ZnO 1.7 ZnO 1.0 Pt 0.7 Al₂O₃ 2.0 A18ZnO 1.7 ZnO 6.0 Pt 0.7 Al₂O₃ 2.0

Each sample was fabricated as follows. First, films to become therespective layers constituting the MR stack 30 were formed in successionby sputtering, for example, to thereby form a multilayer film for the MRstack 30. Next, this multilayer film was subjected to heat treatment.The heat treatment was performed at a temperature of 270° C. for threehours. Next, the multilayer film for the MR stack 30 was patterned byetching to thereby form the MR stack 30. Next, for all the samplesexcept B1 and B3, the first layer 4A, the second layer 4B and the thirdlayer 4C were formed in this order by sputtering to thereby complete thesamples. For the sample B1, instead of forming the first layer 4A, thesecond 4B and the third layer 4C, an insulating film of Al₂O₃ was formedby sputtering to thereby complete the sample. For the sample B3, insteadof forming the first layer 4A, the second 4B and the third layer 4C, asemiconductor film of ZnO and an insulating film of Al₂O₃ were formed inthis order by sputtering to thereby complete the sample. In theexperiment, after completing each sample, the bias magnetic fieldapplying layers 6 were added to each sample.

In the experiment, MR ratio (%) and RA (Ω·μm²) were measured for eachsample. Next, each sample was subjected to a post-sample-fabricationheat treatment. The post-sample-fabrication heat treatment was performedat a temperature of 270° C. for three hours. The post-sample-fabricationheat treatment corresponds to an occasion when heat is applied to the MRelement 5 after fabrication of the MR element 5. Next, MR ratio (%) andRA (Ω·μm²) were again measured for each sample. Here, the state of eachsample before undergoing the post-sample-fabrication heat treatment iscalled an “initial state”, and the state of each sample after undergoingthe post-sample-fabrication heat treatment is called a“post-heat-treatment state”. Furthermore, in the experiment, the valueof MR ratio in the post-heat-treatment state divided by the value of MRratio in the initial state was obtained for each sample. The value thusobtained will be hereinafter called an “MR degradation rate”. A lower MRdegradation rate means a greater reduction in MR ratio resulting fromthe post-sample-fabrication heat treatment as compared with the initialstate. For each sample, Table 4 below lists the MR ratio and RA in theinitial state, the MR ratio and RA in the post-heat-treatment state, andthe MR degradation rate.

TABLE 4 Initial state Post-heat-treatment state MR MR RA MR RAdegradation Sample ratio (%) (Ω · μm²) ratio (%) (Ω · μm²) rate B1 14.50.224 13.5 0.186 0.93 A1 14.7 0.212 14.7 0.209 1.00 A2 14.6 0.203 14.60.201 1.00 A3 14.5 0.194 14.5 0.192 1.00 A4 14.5 0.198 14.5 0.198 1.00A5 14.6 0.196 14.5 0.193 0.99 A6 14.5 0.216 14.4 0.212 0.99 A7 14.70.219 14.7 0.218 1.00 A8 14.6 0.205 14.6 0.204 1.00 A9 14.5 0.199 14.50.195 1.00 A10 14.8 0.218 14.8 0.214 1.00 B2 12.5 0.132 12.3 0.125 0.98B3 11.5 0.120 10.8 0.112 0.94 A11 14.5 0.191 14.5 0.190 1.00 A12 14.60.188 14.5 0.185 0.99 A13 14.7 0.187 14.7 0.187 1.00 A14 14.7 0.181 14.70.178 1.00 A15 14.6 0.185 14.5 0.182 0.99 A16 14.7 0.183 14.7 0.180 1.00B4 12.9 0.141 12.4 0.131 0.96 A17 14.8 0.206 14.8 0.203 1.00 A18 14.50.195 14.5 0.192 1.00

The results of the experiment will now be discussed with reference toTable 3 and Table 4. First, the samples B1 and A1 to A6 are compared. AsTable 4 indicates, the MR degradation rate of the sample B1 is 0.93. Incontrast, the MR degradation rate of each of the samples A1 to A6 is0.99 or 1.00. These results indicate that, whereas an MR elementprovided with an insulating layer of Al₂O₃ instead of the layered film 4(sample B1) suffers a great reduction in MR ratio when heat is appliedto the MR element after its fabrication, it is possible according to theembodiment to suppress a reduction in MR ratio occurring when heat isapplied to the MR element 5 after fabrication of the MR element 5.

Next, the samples A1, A7 to A9 are compared. As Table 3 indicates, thesamples A1, A7 to A9 are different only in thickness of the second layer4B. The thicknesses of the second layer 4B of the samples A1, A7 to A9are 0.7 nm, 0.4 nm, 1.0 nm, and 1.2 nm, respectively. As Table 4indicates, the MR degradation rates of the samples A1, A7 to A9 are all1.00. These results indicate that, in the embodiment, as far as thethickness condition for the second layer 4B is concerned, theabove-described effect can be obtained at least in the 0.4- to 1.2-nmrange.

Next, the samples A1, A10, and B2 are compared. As Table 3 indicates,the samples A1, A10 and B2 are different only in thickness of the thirdlayer 4C. The thicknesses of the third layer 4C of the samples A1, A10,and B2 are 2.0 nm, 1.0 nm, and 0.5 nm, respectively. As Table 4indicates, the MR ratio in the initial state of the sample B2 is muchlower than that of each of the samples A1 and A10. This is presumablybecause in the sample B2 the thickness of the third layer 4C is toosmall and consequently there is a leakage of current from the MR stack30 to the bias magnetic field applying layers 6. These results indicatethat, in the embodiment, as far as the thickness condition for the thirdlayer 4C is concerned, the above-described effect can be obtained atleast in a range not smaller than 1 nm.

Next, the samples A10 and B3 are compared. As Table 3 indicates, thesample B3 has a configuration obtained by eliminating the second layer4B from the configuration of the sample A10. As Table 4 indicates, theMR ratio in the initial state of the sample B3 is much lower than thatof the sample A10. This is presumably because in the sample B3 noSchottky barrier is formed and consequently there is a leakage ofcurrent from the MR stack 30 to the bias magnetic field applying layers6. This result indicates that, in the embodiment, forming a Schottkybarrier at the interface 4AB between the first layer 4A and the secondlayer 4B is effective in suppressing leakage of current from the MRstack 30 to the bias magnetic field applying layers 6.

The experimental results on the samples A11 to A16 will now bedescribed. The samples A11, A13 and A15 are different from the sample A1in the material and thickness of the semiconductor layer 42 and thematerial of the first layer 4A. The samples A12, A14 and A16 aredifferent from the sample A4 in the material and thickness of thesemiconductor layer 42 and the material of the first layer 4A. Each ofthe samples A11 to A16 satisfies the requirements that the first layer4A be formed of the same material as the semiconductor layer 42 and thatthe second layer 4B be a metal layer that forms a Schottky barrier atthe interface 4AB between the first layer 4A and the second layer 4B. Ineach of the samples A11 to A16, the MR degradation rate is 0.99 or 1.00.Furthermore, the MR ratios in the initial state of the samples A11 toA16 are as high as those of the samples A1 and A4. These resultsindicate that, according to the embodiment, it is possible to suppress areduction in MR ratio occurring when heat is applied to the MR element 5after its fabrication and it is possible to suppress leakage of currentfrom the MR stack 30 to the bias magnetic field applying layers 6 viathe layered film 4 as long as the above-described requirements aresatisfied, even if the combination of the material of the semiconductorlayer 42 and the first layer 4A and the material of the second layer 4Bvaries. Next, the samples A1, B4, A17 and A18 are compared. As Table 3indicates, the samples A1, B4, A17 and A18 are different only inthickness of the first layer 4A. The thicknesses of the first layer 4Aof the samples A1, B4, A17 and A18 are 3.0 nm, 0.5 nm, 1.0 nm and 6.0nm, respectively. As Table 4 indicates, the MR ratio in the initialstate of the sample B4 is much lower than that of each of the samplesA1, A17 and A18. This is presumably because in the sample B4 thethickness of the first layer 4A is too small so that a satisfactorySchottky barrier cannot be formed, and consequently there is a leakageof current from the MR stack 30 to the bias magnetic field applyinglayers 6. These results indicate that, in the embodiment, as far as thethickness condition for the first layer 4A is concerned, the previouslydescribed effect can be obtained at least in the 1- to 6-nm range.

A head assembly and a magnetic disk drive of the embodiment will now bedescribed. Reference is first made to FIG. 5 to describe a slider 210incorporated in the head assembly. In the magnetic disk drive, theslider 210 is placed to face toward a magnetic disk platter that is acircular-plate-shaped recording medium to be driven to rotate. Theslider 210 has a base body 211 made up mainly of the substrate 1 and theovercoat layer 17 of FIG. 3. The base body 211 is nearlyhexahedron-shaped. One of the six surfaces of the base body 211 facestoward the magnetic disk platter. The medium facing surface 40 is formedin this one of the surfaces. When the magnetic disk platter rotates inthe z direction of FIG. 5, an airflow passes between the magnetic diskplatter and the slider 210, and a lift is thereby generated below theslider 210 in the y direction of FIG. 5 and exerted on the slider 210.The slider 210 flies over the surface of the magnetic disk platter bymeans of the lift. The x direction of FIG. 5 is across the tracks of themagnetic disk platter. The thin-film magnetic head 100 of the embodimentis formed near the air-outflow-side end (the end located at the lowerleft of FIG. 5) of the slider 210.

Reference is now made to FIG. 6 to describe the head assembly of theembodiment. The head assembly of the embodiment has the slider 210 and asupporter that flexibly supports the slider 210. Forms of this headassembly include a head gimbal assembly and a head arm assemblydescribed below.

The head gimbal assembly 220 will be first described. The head gimbalassembly 220 has the slider 210 and a suspension 221 as the supporterthat flexibly supports the slider 210. The suspension 221 has: aplate-spring-shaped load beam 222 made of stainless steel, for example;a flexure 223 to which the slider 210 is joined, the flexure 223 beinglocated at an end of the load beam 222 and giving an appropriate degreeof freedom to the slider 210; and a base plate 224 located at the otherend of the load beam 222. The base plate 224 is attached to an arm 230of an actuator for moving the slider 210 along the x direction acrossthe tracks of the magnetic disk platter 262. The actuator has the arm230 and a voice coil motor that drives the arm 230. A gimbal section formaintaining the orientation of the slider 210 is provided in the portionof the flexure 223 on which the slider 210 is mounted.

The head gimbal assembly 220 is attached to the arm 230 of the actuator.An assembly including the arm 230 and the head gimbal assembly 220attached to the arm 230 is called a head arm assembly. An assemblyincluding a carriage having a plurality of arms wherein the head gimbalassembly 220 is attached to each of the arms is called a head stackassembly.

FIG. 6 illustrates the head arm assembly of the embodiment. In the headarm assembly, the head gimbal assembly 220 is attached to an end of thearm 230. A coil 231 that is part of the voice coil motor is fixed to theother end of the arm 230. A bearing 233 is provided in the middle of thearm 230. The bearing 233 is attached to a shaft 234 that rotatablysupports the arm 230.

Reference is now made to FIG. 7 and FIG. 8 to describe an example of thehead stack assembly and the magnetic disk drive of the embodiment. FIG.7 is an explanatory view illustrating the main part of the magnetic diskdrive, and FIG. 8 is a top view of the magnetic disk drive. The headstack assembly 250 incorporates a carriage 251 having a plurality ofarms 252. A plurality of head gimbal assemblies 220 are attached to thearms 252 such that the assemblies 220 are arranged in the verticaldirection with spacing between respective adjacent ones. A coil 253 thatis part of the voice coil motor is mounted on the carriage 251 on a sideopposite to the arms 252. The head stack assembly 250 is installed inthe magnetic disk drive. The magnetic disk drive includes a plurality ofmagnetic disk platters 262 mounted on a spindle motor 261. Two of thesliders 210 are allocated to each of the platters 262, such that the twosliders 210 are opposed to each other with each of the platters 262disposed in between. The voice coil motor includes permanent magnets 263disposed to be opposed to each other, the coil 253 of the head stackassembly 250 being placed between the magnets 263.

The actuator and the head stack assembly 250 except the sliders 210correspond to the alignment device of the invention, and support thesliders 210 and align them with respect to the magnetic disk platters262.

In the magnetic disk drive of the embodiment, the actuator moves theslider 210 across the tracks of the magnetic disk platter 262 and alignsthe slider 210 with respect to the magnetic disk platter 262. Thethin-film magnetic head incorporated in the slider 210 writes data onthe magnetic disk platter 262 by using the write head, and reads datastored on the magnetic disk platter 262 by using the read head.

The head assembly and the magnetic disk drive of the embodiment exhibiteffects similar to those of the thin-film magnetic head of theembodiment described previously.

The present invention is not limited to the foregoing embodiment butvarious modifications are possible. For example, the pinned layer 23 isnot limited to a synthetic pinned layer. In addition, while theembodiment has been described with reference to a thin-film magnetichead having a structure in which the read head is formed on the basebody and the write head is stacked on the read head, the read head andthe write head may be stacked in the reverse order.

When the thin-film magnetic head is to be used only for read operations,the magnetic head may be configured to include the read head only.

It is apparent that the present invention can be carried out in variousforms and modifications in the light of the foregoing descriptions.Accordingly, within the scope of the following claims and equivalentsthereof, the present invention can be carried out in forms other thanthe foregoing most preferable embodiments.

1. A magnetoresistive element comprising an MR stack including a firstferromagnetic layer, a second ferromagnetic layer, and a spacer layerdisposed between the first ferromagnetic layer and the secondferromagnetic layer, wherein: a current for detecting magnetic signalsis fed in a direction intersecting a plane of each of the foregoinglayers; the MR stack has an outer surface; and the spacer layer has aperiphery located in the outer surface of the MR stack; themagnetoresistive element further comprising a layered film that touchesthe periphery of the spacer layer, wherein: the spacer layer includes asemiconductor layer formed using an oxide semiconductor as a material;the layered film includes a first layer, a second layer, and a thirdlayer stacked in this order; the first layer is formed of the samematerial as the semiconductor layer, and touches the periphery of thespacer layer; the second layer is a metal layer that forms a Schottkybarrier at an interface between the first layer and the second layer;and the third layer is an insulating layer.
 2. The magnetoresistiveelement according to claim 1, wherein the first ferromagnetic layer is afree layer having a direction of magnetization that changes in responseto an external magnetic field, while the second ferromagnetic layer is apinned layer having a fixed direction of magnetization.
 3. Themagnetoresistive element according to claim 1, wherein the first layerhas a thickness within a range of 1 to 6 nm.
 4. The magnetoresistiveelement according to claim 1, wherein the second layer has a thicknesswithin a range of 0.4 to 1.2 nm.
 5. The magnetoresistive elementaccording to claim 1, wherein the third layer has a thickness of 1 nm orgreater.
 6. The magnetoresistive element according to claim 1, whereinthe material of which the semiconductor layer and the first layer areformed is an oxide of at least one of Zn, In and Sn.
 7. Themagnetoresistive element according to claim 1, wherein the material ofwhich the semiconductor layer and the first layer are formed is ZnO,while a material of which the second layer is formed is any of Os, Ir,Pt, Pd, Ni, Au, Co and Ru.
 8. A thin-film magnetic head comprising: amedium facing surface that faces toward a recording medium; amagnetoresistive element disposed near the medium facing surface todetect a signal magnetic field sent from the recording medium; and apair of electrodes for feeding a current for detecting magnetic signalsto the magnetoresistive element, wherein: the magnetoresistive elementcomprises an MR stack including a first ferromagnetic layer, a secondferromagnetic layer, and a spacer layer disposed between the firstferromagnetic layer and the second ferromagnetic layer; in themagnetoresistive element, the current for detecting magnetic signals isfed in a direction intersecting a plane of each of the foregoing layers;the MR stack has an outer surface; the spacer layer has a peripherylocated in the outer surface of the MR stack; the magnetoresistiveelement further comprises a layered film that touches the periphery ofthe spacer layer; the spacer layer includes a semiconductor layer formedusing an oxide semiconductor as a material; the layered film includes afirst layer, a second layer, and a third layer stacked in this order;the first layer is formed of the same material as the semiconductorlayer, and touches the periphery of the spacer layer; the second layeris a metal layer that forms a Schottky barrier at an interface betweenthe first layer and the second layer; and the third layer is aninsulating layer.
 9. A thin-film magnetic head comprising a mediumfacing surface that faces toward a recording medium, a read head, and awrite head, wherein: the read head comprises a magnetoresistive elementdisposed near the medium facing surface to detect a signal magneticfield sent from the recording medium, and a pair of electrodes forfeeding a current for detecting magnetic signals to the magnetoresistiveelement; the magnetoresistive element comprises an MR stack including afirst ferromagnetic layer, a second ferromagnetic layer, and a spacerlayer disposed between the first ferromagnetic layer and the secondferromagnetic layer; in the magnetoresistive element, the current fordetecting magnetic signals is fed in a direction intersecting a plane ofeach of the foregoing layers; the MR stack has an outer surface; thespacer layer has a periphery located in the outer surface of the MRstack; the magnetoresistive element further comprises a layered filmthat touches the periphery of the spacer layer; the spacer layerincludes a semiconductor layer formed using an oxide semiconductor as amaterial; the layered film includes a first layer, a second layer, and athird layer stacked in this order; the first layer is formed of the samematerial as the semiconductor layer, and touches the periphery of thespacer layer; the second layer is a metal layer that forms a Schottkybarrier at an interface between the first layer and the second layer;and the third layer is an insulating layer.
 10. A method ofmanufacturing a thin-film magnetic head, the thin-film magnetic headcomprising a medium facing surface that faces toward a recording medium,a read head, and a write head, wherein: the read head comprises amagnetoresistive element disposed near the medium facing surface todetect a signal magnetic field sent from the recording medium, and apair of electrodes for feeding a current for detecting magnetic signalsto the magnetoresistive element; the magnetoresistive element comprisesan MR stack including a first ferromagnetic layer, a secondferromagnetic layer, and a spacer layer disposed between the firstferromagnetic layer and the second ferromagnetic layer; in themagnetoresistive element, the current for detecting magnetic signals isfed in a direction intersecting a plane of each of the foregoing layers;the MR stack has an outer surface; the spacer layer has a peripherylocated in the outer surface of the MR stack; the magnetoresistiveelement further comprises a layered film that touches the periphery ofthe spacer layer; the spacer layer includes a semiconductor layer formedusing an oxide semiconductor as a material; the layered film includes afirst layer, a second layer, and a third layer stacked in this order;the first layer is formed of the same material as the semiconductorlayer, and touches the periphery of the spacer layer; the second layeris a metal layer that forms a Schottky barrier at an interface betweenthe first layer and the second layer; and the third layer is aninsulating layer, the method comprising the steps of: forming the readhead; and forming the write head after the read head is formed, whereinthe step of forming the write head includes the step of performing heattreatment.
 11. A head assembly comprising: a slider including athin-film magnetic head and disposed to face toward a recording medium;and a supporter flexibly supporting the slider, wherein: the thin-filmmagnetic head comprises: a medium facing surface that faces toward therecording medium; a magnetoresistive element disposed near the mediumfacing surface to detect a signal magnetic field sent from the recordingmedium; and a pair of electrodes for feeding a current for detectingmagnetic signals to the magnetoresistive element; the magnetoresistiveelement comprises an MR stack including a first ferromagnetic layer, asecond ferromagnetic layer, and a spacer layer disposed between thefirst ferromagnetic layer and the second ferromagnetic layer; in themagnetoresistive element, the current for detecting magnetic signals isfed in a direction intersecting a plane of each of the foregoing layers;the MR stack has an outer surface; the spacer layer has a peripherylocated in the outer surface of the MR stack; the magnetoresistiveelement further comprises a layered film that touches the periphery ofthe spacer layer; the spacer layer includes a semiconductor layer formedusing an oxide semiconductor as a material; the layered film includes afirst layer, a second layer, and a third layer stacked in this order;the first layer is formed of the same material as the semiconductorlayer, and touches the periphery of the spacer layer; the second layeris a metal layer that forms a Schottky barrier at an interface betweenthe first layer and the second layer; and the third layer is aninsulating layer.
 12. A magnetic disk drive comprising: a sliderincluding a thin-film magnetic head and disposed to face toward arecording medium that is driven to rotate; and an alignment devicesupporting the slider and aligning the slider with respect to therecording medium, wherein: the thin-film magnetic head comprises: amedium facing surface that faces toward the recording medium; amagnetoresistive element disposed near the medium facing surface todetect a signal magnetic field sent from the recording medium; and apair of electrodes for feeding a current for detecting magnetic signalsto the magnetoresistive element; the magnetoresistive element comprisesan MR stack including a first ferromagnetic layer, a secondferromagnetic layer, and a spacer layer disposed between the firstferromagnetic layer and the second ferromagnetic layer; in themagnetoresistive element, the current for detecting magnetic signals isfed in a direction intersecting a plane of each of the foregoing layers;the MR stack has an outer surface; the spacer layer has a peripherylocated in the outer surface of the MR stack; the magnetoresistiveelement further comprises a layered film that touches the periphery ofthe spacer layer; the spacer layer includes a semiconductor layer formedusing an oxide semiconductor as a material; the layered film includes afirst layer, a second layer, and a third layer stacked in this order;the first layer is formed of the same material as the semiconductorlayer, and touches the periphery of the spacer layer; the second layeris a metal layer that forms a Schottky barrier at an interface betweenthe first layer and the second layer; and the third layer is aninsulating layer.